A systematic study of Fagraea Sensu Lato and a revision of the Peninsular Malaysian Taxa / Sugumaran Manickam

Manickam, Sugumaran (2010) A systematic study of Fagraea Sensu Lato and a revision of the Peninsular Malaysian Taxa / Sugumaran Manickam. PhD thesis, University of Malaya.

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Abstract

systematic study of the Peninsular Malaysian species of Fagraea sensu lato was undertaken. This was done in the light of recent revisionary work done for Borneo that documented 20 new species and demonstrated that previous species concepts for Fagraea were too broad. Parallel to this the distinction of the subgeneric groups recognised as sections, i.e., Cyrtophyllum, Fagraea and Racemosae, were investigated with molecular phylogenetic methods. Representative taxa from the Malay Peninsula and Borneo augmented by sequences from other taxa in the same subtribe and tribe were used in the molecular analysis. Gene sequences from ITS, trnL–F (trnL intron + trnL–F spacer) and ndhF were analysed with two methods viz., maximum parsimony and Bayesian analyses. The results indicate that Fagraea s.l. includes four well-supported monophyletic groups, with the several gene sequences analysed with two phylogenetic methods. Two of the clades, viz., Fagraea and Racemosa, could be equated to sections Fagraea and Racemosae, respectively. The remaining two clades, viz., Elliptica and Gigantea appear to be parts of the section Cyrtophyllum. The Racemosa clade had the most morphological synapomorphies, with a distinct plant architecture where trunk growth is continuous and branches are plagiotropic (with distichous leaf arrangement); pendulous inflorescences; and a firm fruit wall with an epidermis that does not detach and wrinkle upon drying. The Fagraea clade (excluding Fagraea crenulata) has fruits that produce copious creamy pale yellowish latex in the fruit epidermis and fruit wall and have ellipsoid-rounded seeds. In comparison, all the other species of Fagraea (including F. crenulata) either have no latex or produce small amounts of translucent gummy latex and have polygonal seeds. F. crenulata is aberrant in the Fagraea clade in having unique characters such as a distinct architectural model, thorny bark and crenulate leaf margins. It is however, related to the Fagraea clade in having petiolar sheaths that do not or only slightly fuse at the edges and a peltate stigma structure. Phylogenetic analyses with the ITS region did not include F. crenulata in the Fagraea clade. However, F. crenulata is resolved basal to the Fagraea clade with chloroplast gene analyses. The clear split of section Cyrtophyllum into the Gigantea and Elliptica clades was somewhat surprising as these groups have a number of similar morphological features, such as small flowers and muchprotruding stamens and styles. In comparison, the other groups are generally distinguishable with bigger flowers and less exserted stamens and styles. The only morphological difference between these two groups is the position of the inflorescence, terminal in Elliptica and axillary in Gigantea. Recognition of Fagraea s.l. as four distinct genera is indicated, as the complex is considered morphologically too divergent to be regarded as a single genus. These correspond to the four clades recognised in the molecular analyses, viz., Elliptica, Fagraea, Gigantea and Racemosa, and could adopt Picrophloeus Bl., Fagraea Thunb. (sensu stricto), Cyrtophyllum Reinw. ex Bl. and Utania G.Don, respectively, as good genus names. The position of F. crenulata is doubtful and it is provisionally maintained in Fagraea s.s. pending future molecular investigations with a larger taxon sampling over wider geographical context, and the use of further gene regions.

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